Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

A heat transfer oil, comprising: a. a base oil fraction have a traction
coefficient less than or equal to 0.015, when measured at a kinematic
viscosity of 15 cSt and at a slide to roll ratio of 40 percent; and b.
optionally, an antifoam agent; wherein the heat transfer oil has an auto
ignition temperature greater than 329° C. (625° F.) and an
ASTM Color less than 0.5.

Claims:

1. A heat transfer oil, comprising:a. a base oil fraction have a traction
coefficient less than or equal to 0.015, when measured at a kinematic
viscosity of 15 cSt and at a slide to roll ratio of 40 percent; andb. an
antifoam agent; wherein the heat transfer oil has an auto ignition
temperature greater than 329.degree. C. (625.degree. F.) and an ASTM
Color less than 0.5.

2. The heat transfer oil of claim 1, wherein the base oil was produced by
isomerization.

4. The heat transfer oil of claim 1, where the base oil fraction has a 50
wt % boiling point greater than 566.degree. C.

5. The heat transfer oil of claim 1, wherein the base oil fraction has a
traction coefficient less than or equal to 0.011, when measured at a
kinematic viscosity of 15 cSt and at a slide to roll ratio of 40 percent.

7. The heat transfer oil of claim 1, wherein the auto ignition temperature
is additionally greater than an amount defined by the equation:
AIT=1.6.times.(Kinematic Viscosity at 40.degree. C., in cSt)+300, in
degrees Celsius.

14. A heat transfer oil, comprising:a. a base oil fraction have a traction
coefficient less than or equal to 0.015, when measured at a kinematic
viscosity of 15 cSt and at a slide to roll ratio of 40 percent; andb.
optionally, an antifoam agent; wherein the heat transfer oil has an auto
ignition temperature greater than 329.degree. C. (625.degree. F.) and is
colorless by the ASTM Color test.

17. The heat transfer oil of claim 14, wherein the antifoam agent is
selected from the group consisting of high molecular weight polydimethyl
siloxane, acrylate, and mixtures thereof.

18. The heat transfer oil of claim 14, wherein the auto ignition
temperature is additionally greater than an amount defined by the
equation: AIT=1.6.times.(Kinematic Viscosity at 40.degree. C., in
cSt)+300, in degrees Celsius.

19. The heat transfer oil of claim 14, wherein the base oil was produced
by isomerization.

Description:

[0001]This application is a divisional of U.S. patent application Ser. No.
11/535,165, filed on Sep. 26, 2006. It relates to two co-filed patent
applications titled "Method of Using Heat Transfer Oil Having High Auto
Ignition Temperature" and "Process to Prepare a Heat Transfer Oil."

FIELD OF THE INVENTION

[0002]This invention is directed to a heat transfer oil having a high auto
ignition temperature made using a base oil with a very low traction
coefficient.

BACKGROUND OF THE INVENTION

[0003]Heat transfer oils should never be used above their auto ignition
temperature (AIT). AIT is the temperature at which the fluid will ignite
spontaneously in contact with air. Highly paraffinic heat transfer oils
such as Caloria HT43, Mobiltherm 603, and Duratherm 630 have AITs of
632° F., 670° F., and 693° F., respectively. These
known heat transfer oils are made with highly refined, severely
hydrotreated, petroleum-based paraffin oils that do not have the high
viscosity index and preferred molecular composition that are desired.
Conventional heat transfer oils made by Chevron using petroleum derived
neutral oils have AIT's of approximately 599° F. A heat transfer
oil, made using a base oil made from a waxy feed, and having a higher
auto ignition temperature and higher viscosity index is desired; and
processes to make and use it are also desired.

SUMMARY OF THE INVENTION

[0004]We have invented a heat transfer oil, comprising a base oil made
from a waxy feed. The base oil has a pour point less than -9° C.,
less than 0.3 wt % aromatics, greater than 10 weight percent and less
than 70 weight percent total molecules with cycloparaffinic
functionality, and a ratio of molecules with monocycloparaffinic
functionality to molecules with multicycloparaffinic functionality
greater than 15. The heat transfer oil has an AIT greater than
329° C. (625° F.), a viscosity index greater than
28×Ln (Kinematic Viscosity at 100° C., in cSt), and is
selected from the group consisting of ISO 10, ISO 15, ISO 22, ISO 46, ISO
68, ISO 100, ISO 150, and ISO 220.

[0005]We have also invented a process to prepare a heat transfer oil,
comprising: dewaxing a substantially paraffinic wax feed by
hydroisomerization dewaxing using a shape selective intermediate pore
size molecular sieve under hydroisomerization conditions including a
hydrogen to feed ratio from about 712.4 to about 3562 liter H2/liter
oil (about 4 to about 20 MSCF/bbl), whereby a lubricating base oil is
produced, [0006]a. selecting one or more fractions of the lubricating
base oil having: [0007]i. a pour point less than -9° C.,
[0008]ii. greater than 10 weight percent and less than 70 weight percent
total molecules with cycloparaffinic functionality, and [0009]iii. a
ratio of weight percent molecules with monocycloparaffinic functionality
to weight percent molecules with multicycloparaffinic functionality
greater than 15; and [0010]b. blending the one or more fractions of the
lubricating base oil with less than 0.2 wt % antifoam agent to prepare
the heat transfer oil of an ISO viscosity grade selected from the group
of ISO 10, ISO 15, ISO 22, ISO 46, ISO 68, ISO 100, ISO 150, and ISO 220.

[0011]We have also invented a method to use a heat transfer oil,
comprising: [0012]a. selecting a heat transfer oil having an auto
ignition temperature greater than 329° C. (625° F.) and a
viscosity index greater than 28×Ln (Kinematic Viscosity at
100° C., in cSt)+80; wherein the heat transfer oil comprises a
base oil, made from a waxy feed, having: [0013]i. greater than 10 weight
percent and less than 70 weight percent total molecules with
cycloparaffinic functionality; [0014]b. providing the heat transfer oil
to a mechanical system; and [0015]c. transferring heat in the mechanical
system from a heat source to a heat sink.

[0016]In another embodiment, we have invented a heat transfer oil,
comprising: [0017]a. a base oil fraction have a traction coefficient
less than or equal to 0.015, when measured at a kinematic viscosity of 15
cSt and at a slide to roll ratio of 40 percent; and [0018]b. an antifoam
agent; [0019]wherein the heat transfer oil has an auto ignition
temperature greater than 329° C. (625° F.) and an ASTM
Color less than 0.5.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 illustrates the plot of Kinematic Viscosity at 40° C.
in cSt vs. Auto Ignition Temperature by ASTM E659-78(Reapproved 2005) in
degrees Celsius. It shows the line for the auto ignition temperature
equal to 1.6×(Kinematic Viscosity at 40° C.)+300.

[0021]FIG. 2 illustrates the plot of ISO Viscosity Grade vs. 5 wt %
boiling point by ASTM D6352-04, in degrees Celsius. It shows the line for
the 5 wt % boiling point equal to 1.3×(ISO Viscosity Grade)+360.

[0022]FIG. 3 illustrates the plots of Kinematic Viscosity at 100°
C. in cSt vs. two preferred viscosity index lines, one being the equation
for viscosity index equal to 28×Ln (Kinematic Viscosity at
100° C.)+80 and the other being the equation for viscosity index
equal to 28×Ln (Kinematic Viscosity at 100° C.)+95.

DETAILED DESCRIPTION OF THE INVENTION

[0023]We have discovered that heat transfer oils made using base oil
having low pour point, low aromatic content, defined cycloparaffinic
content, and a high ratio of monocycloparaffins to multicycloparaffins
have an exceptionally high viscosity index (VI) and auto ignition
temperature (AIT). In addition, they have comparable Ramsbottom carbon
residues, and improved simulated distillation profiles.

[0024]Weight percent Ramsbottom carbon residue is measured by ASTM D
524-04. The carbon residue is the residue formed by evaporation and
thermal degradation of a carbon containing material. A low Ramsbottom
carbon residue is an indication of the relative coke-forming propensity
of a heat transfer oil, and is desired to be as low as possible in the
heat transfer oil while still retaining a low auto ignition temperature.

[0025]The term "Ln" in the context of equations in this disclosure refers
to the natural logarithm with base `e`. The terms "Fischer-Tropsch
derived" or "FT derived" means that the product, fraction, or feed
originates from or is produced at some stage by a Fischer-Tropsch
process. The term "substantially paraffinic" means containing a high
level of n-paraffins, generally greater than 40 wt %, preferably greater
than 50 wt %, more preferably greater than 75 wt %.

[0027]Slack wax can be obtained from conventional petroleum derived
feedstocks by either hydrocracking or by solvent refining of the lube oil
fraction. Typically, slack wax is recovered from solvent dewaxing
feedstocks prepared by one of these processes. Hydrocracking is usually
preferred because hydrocracking will also reduce the nitrogen content to
a low value. With slack wax derived from solvent refined oils, deoiling
may be used to reduce the nitrogen content. Hydrotreating of the slack
wax can be used to lower the nitrogen and sulfur content. Slack waxes
posses a very high viscosity index, normally in the range of from about
140 to 200, depending on the oil content and the starting material from
which the slack wax was prepared. Therefore, slack waxes are suitable for
the preparation of base oils made from a waxy feed used in the heat
transfer oils of this invention.

[0028]The waxy feed useful in this invention preferably has less than 25
ppm total combined nitrogen and sulfur. Nitrogen is measured by melting
the waxy feed prior to oxidative combustion and chemiluminescence
detection by ASTM D 4629-02. The test method is further described in U.S.
Pat. No. 6,503,956, incorporated herein. Sulfur is measured by melting
the waxy feed prior to ultraviolet fluorescence by ASTM D 5453-00. The
test method is further described in U.S. Pat. No. 6,503,956, incorporated
herein.

[0029]Determination of normal paraffins (n-paraffins) in wax-containing
samples should use a method that can determine the content of individual
C7 to C110 n-paraffins with a limit of detection of 0.1 wt %. The
preferred method used is described later in this disclosure.

[0030]Waxy feeds useful in this invention are expected to be plentiful and
relatively cost competitive in the near future as large-scale
Fischer-Tropsch synthesis processes come into production. Syncrude
prepared from the Fischer-Tropsch process comprises a mixture of various
solid, liquid, and gaseous hydrocarbons. Those Fischer-Tropsch products
which boil within the range of lubricating base oil contain a high
proportion of wax which makes them ideal candidates for processing into
base oil. Accordingly, Fischer-Tropsch wax represents an excellent feed
for preparing high quality base oils according to the process of the
invention. Fischer-Tropsch wax is normally solid at room temperature and,
consequently, displays poor low temperature properties, such as pour
point and cloud point. However, following hydroisomerization of the wax,
Fischer-Tropsch derived base oils having excellent low temperature
properties may be prepared. A general description of suitable
hydroisomerization dewaxing processes may be found in U.S. Pat. Nos.
5,135,638 and 5,282,958; and US Patent Application 20050133409,
incorporated herein.

[0032]The hydroisomerizing conditions depend on the waxy feed used, the
hydroisomerization catalyst used, whether or not the catalyst is
sulfided, the desired yield, and the desired properties of the base oil.
Preferred hydroisomerizing conditions useful in the current invention
include temperatures of 260 degrees C. to about 413 degrees C. (500 to
about 775 degrees F.), a total pressure of 15 to 3000 psig, and a
hydrogen to feed ratio from about 2 to 30 MSCF/bbl, preferably from about
4 to 20 MSCF/bbl (about 712.4 to about 3562 liter H2/liter oil),
more preferably from about 4.5 or 5 to about 10 MSCF/bbl, most preferably
from about 5 to about 8 MSCF/bbl. Generally, hydrogen will be separated
from the product and recycled to the isomerization zone. Note that a feed
rate of 10 MSCF/bbl is equivalent to 1781 liter H2/liter feed. Generally,
hydrogen will be separated from the product and recycled to the
isomerization zone.

[0033]Optionally, the base oil produced by hydroisomerization dewaxing may
be hydrofinished. The hydrofinishing may occur in one or more steps,
either before or after fractionating of the base oil into one or more
fractions. The hydrofinishing is intended to improve the oxidation
stability, UV stability, and appearance of the product by removing
aromatics, olefins, color bodies, and solvents. A general description of
hydrofinishing may be found in U.S. Pat. Nos. 3,852,207 and 4,673,487,
incorporated herein. The hydrofinishing step may be needed to reduce the
weight percent olefins in the base oil to less than 10, preferably less
than 5 or 2, more preferably less than 1 even more preferably less than
0.5, and most preferably less than 0.05 or 0.01 The hydrofinishing step
may also be needed to reduce the weight percent aromatics to less than
0.3 or 0.1, preferably less than 0.05, more preferably less than 0.02,
and most preferably less than 0.01.

[0034]The lubricating base oil is typically separated into fractions,
whereby one or more of the fractions will have a pour point less than
-9° C., a total weight percent of molecules with cycloparaffinic
functionality greater than 10, and a ratio of weight percent molecules
with monocycloparaffinic functionality to weight percent molecules with
multicycloparaffinic functionality greater than 15. The base oil is
optionally fractionated into different viscosity grades of base oil. In
the context of this disclosure "different viscosity grades of base oil"
is defined as two or more base oils differing in kinematic viscosity at
100 degrees C. from each other by at least 1.0 cSt. Kinematic viscosity
is measured using ASTM D 445-04. Fractionating is done using a vacuum
distillation unit to yield cuts with pre selected boiling ranges. One of
the fractions may be a distillation bottoms product.

[0035]The base oil fractions will typically have a pour point less than
zero degrees C. Preferably the pour point will be less than -9 degrees C.
Additionally, in some embodiments the pour point of the base oil fraction
will have a ratio of pour point, in degrees C., to the kinematic
viscosity at 100 degrees C., in cSt, greater than a Base Oil Pour Factor,
where the Base Oil Pour Factor is defined by the equation: Base Oil Pour
Factor=7.35×Ln (Kinematic Viscosity at 100° C.)-18. Pour
point is measured by ASTM D 5950-02.

[0036]The base oil fractions have measurable quantities of unsaturated
molecules measured by FIMS. In a preferred embodiment the
hydroisomerization dewaxing and fractionating conditions in the process
of this invention are tailored to produce one or more selected fractions
of base oil having greater than 10 weight percent total molecules with
cycloparaffinic functionality, preferably greater than 20 weight percent,
more preferably greater than 35 or greater than 40; and a viscosity index
greater than 150. The one or more selected fractions of base oils will
usually have less than 70 weight percent total molecules with
cycloparaffinic functionality. Preferably the one or more selected
fractions of base oil will additionally have a ratio of molecules with
monocycloparaffinic functionality to molecules with multicycloparaffinic
functionality greater than 2.1, more preferably greater than 15. In some
preferred embodiments there may be no molecules with multicycloparaffinic
functionality, such that the ratio of molecules with monocycloparaffinic
functionality to molecules with multicycloparaffinic functionality is
greater than 100.

[0037]The viscosity indexes of the lubricating base oils used in the heat
transfer oils of this invention will be high. They will generally have
viscosity indexes greater than 28×Ln (Kinematic Viscosity at
100° C.)+80. in a preferred embodiment they will have viscosity
indexes greater than 28×Ln (Kinematic Viscosity at 100°
C.)+95. Plots for the lines that define the two lower limits for the
viscosity indexes described above are shown in FIG. 3. For example a 4.5
cSt oil will have a viscosity index greater than 122, preferably greater
than 137; and a 6.5 cSt oil will have a viscosity index greater than 132,
preferably greater than 147. The test method used to measure viscosity
index is ASTM D 2270-04.

[0038]The presence of predominantly cycloparaffinic molecules with
monocycloparaffinic functionality in the base oil fractions of this
invention provides excellent oxidation stability, low Noack volatility,
as well as desired additive solubility and elastomer compatibility. The
base oil fractions have a weight percent olefins less than 10, preferably
less than 5, more preferably less than 1, even more preferably less than
0.5, and most preferably less than 0.05 or 0.01. The base oil fractions
preferably have a weight percent aromatics less than 0.1, more preferably
less than 0.05, and most preferably less than 0.02. Heat transfer oils
made with a base oil with low olefin and aromatic contents would also
have higher oxidation stabilities and should give longer service lives
than heat transfer oils made with other paraffinic base oils.

[0039]In preferred embodiments, the base oil fractions have a traction
coefficient less than 0.023, preferably less than or equal to 0.021, more
preferably less than or equal to 0.019, when measured at a kinematic
viscosity of 15 cSt and at a slide to roll ratio of 40 percent.
Preferably they have a traction coefficient less than an amount defined
by the equation: traction coefficient=0.009×Ln (Kinematic
Viscosity)-0.001, wherein the Kinematic Viscosity during the traction
coefficient measurement is between 2 and 50 cSt; and wherein the traction
coefficient is measured at an average rolling speed of 3 meters per
second, a slide to roll ratio of 40 percent, and a load of 20 Newtons. In
one embodiment the base oil fractions have a traction coefficient less
than 0.015 or 0.011, when measured at a kinematic viscosity of 15 cSt and
at a slide to roll ratio of 40 percent. Examples of these preferred base
oil fractions with low traction coefficients are taught in U.S. Pat. No.
7,045,055 and U.S. patent application Ser. No. 11/400570, filed Apr. 7,
2006.

[0040]In preferred embodiments, where the olefin and aromatics contents
are significantly low in the lubricant base oil fraction of the
lubricating oil, the Oxidator BN of the selected base oil fraction will
be greater than 25 hours, preferably greater than 35 hours, more
preferably greater than 40 or even 41 hours. The Oxidator BN of the
selected base oil fraction will typically be less than 65 hours. Oxidator
BN is a convenient way to measure the oxidation stability of base oils.
The Oxidator BN test is described by Stangeland et al. in U.S. Pat. No.
3,852,207. The Oxidator BN test measures the resistance to oxidation by
means of a Dornte-type oxygen absorption apparatus. See R. W. Dornte
"Oxidation of White Oils," Industrial and Engineering Chemistry, Vol. 28,
page 26, 1936. Normally, the conditions are one atmosphere of pure oxygen
at 340° F. The results are reported in hours to absorb 1000 ml of
O2 by 100 g. of oil. In the Oxidator BN test, 0.8 ml of catalyst is used
per 100 grams of oil and an additive package is included in the oil. The
catalyst is a mixture of soluble metal naphthenates in kerosene. The
mixture of soluble metal naphthenates simulates the average metal
analysis of used crankcase oil. The level of metals in the catalyst is as
follows: Copper=6,927 ppm; Iron=4,083 ppm; Lead=80,208 ppm; Manganese=350
ppm; Tin=3565 ppm. The additive package is 80 millimoles of zinc
bispolypropylenephenyidithio-phosphate per 100 grams of oil, or
approximately 1.1 grams of OLOA 260. The Oxidator BN test measures the
response of a lubricating base oil in a simulated application. High
values, or long times to absorb one liter of oxygen, indicate good
oxidation stability.

[0041]OLOA is an acronym for Oronite Lubricating Oil Additive®, which
is a registered trademark of Chevron Oronite.

[0042]Antifoam Agent:

[0043]Foam tendency and stability are measured by ASTM D 892-03. ASTM D
892-03 measures the foaming characteristics of a lubricating base oil or
finished lubricant at 24 degrees C. and 93.5 degrees C. It provides a
means of empirically rating the foaming tendency and stability of the
foam. The test oil, maintained at a temperature of 24 degrees C., is
blown with air at a constant rate for 5 minutes then allowed to settle
for 10 minutes. The volume of foam, in ml, is measured at the end of both
periods (sequence I). The foaming tendency is provided by the first
measurement, the foam stability by the second measurement. The test is
repeated using a new portion of the test oil at 93.5 degrees C. (sequence
II); however the settling time is reduced to one minute. For ASTM D
892-03 sequence III the same sample is used from sequence II, after the
foam has collapsed and cooled to 24 degrees C. The test oil is blown with
dry air for 5 minutes, and then settled for 10 minutes. The foam tendency
and stability are again measured, and reported in ml. A good quality heat
transfer oil will generally have less than 100 ml foam tendency for each
of sequence I, II, and III; and zero ml foam stability for each of
sequence I, II, and III; the lower the foam tendency of a lubricating
base oil or heat transfer oil the better. The heat transfer oils of this
invention have much lower foaming tendency than typical heat transfer
oils. They preferably have a sequence I foam tendency less than 50 ml;
they have a sequence II foam tendency less than 50 ml, preferably less
than 30 ml; and they preferably have a sequence III foam tendency less
than 50 ml.

[0044]Foaming will vary in different base oils but can be controlled by
the addition of antifoam agents. Generally, the heat transfer oils of
this invention will be blended little to no antifoam agent, typically
less than 0.2 wt %. However, heat transfer oils of a higher viscosity or
additionally comprising other base oils may exhibit foaming. Examples of
antifoam agents are silicone oils, polyacrylates, acrylic polymers, and
fluorosilicones.

[0045]Antifoam agents work by destabilizing the liquid film that surrounds
entrained air bubbles. To be effective they must spread effectively at
the air/liquid interface. According to theory, the antifoam agent will
spread if the value of the spreading coefficient, S, is positive. S is
defined by the following equation: S=p1-p2-p1,2, wherein p1 is the
surface tension of the foamy liquid, p2 is the surface tension of the
antifoam agent, and p1,2 is the interfacial tension between them. Surface
tension and interfacial tensions are measured using a ring type
tensiometer by ASTM D 1331-89 (Reapproved 2001), "Surface and Interfacial
Tension of Solutions of Surface-Active Agents". With respect to the
current invention, p1 is the surface of the heat transfer oil prior to
the addition of antifoam agent.

[0046]Preferred choices of antifoam agents in the heat transfer oils of
this invention are antifoam agents that when blended into the heat
transfer oil will exhibit spreading coefficients of at least 2 mN/m at
both 24 degrees C. and 93.5 degrees C. Various types of antifoam agents
are taught in U.S. Pat. No. 6,090,758. When used, the antifoam agents
should not significantly increase the air release time of the heat
transfer oil. One preferred antifoam agent is high molecular weight
polydimethyl siloxane, a type of silicone antifoam agent. Another
preferred choice of antifoam agent in the heat transfer oils of this
invention are acrylate antifoam agents, as they are less likely to
adversely effect air release properties compared to lower molecular
weight silicone antifoam agents.

[0047]The heat transfer oils of this invention may have ISO viscosity
grades of 10 to 220. The ISO viscosity grades are defined by ASTM D
2422-97 (Reapproved 2002). The heat transfer oils of this invention also
have 5 wt % boiling points relative to their ISO viscosity grades that
are higher than other earlier known paraffinic type heat transfer oils.
In one preferred embodiment the heat transfer oil will have a 5 wt %
boiling point greater than 1.3×(ISO Grade of Heat Transfer
Oil)+360, in ° C. A plot of the line defining this preferred lower
limit of the 5 wt % boiling point of this embodiment of the heat transfer
oils of this invention is shown in FIG. 2. More preferably, for example,
an ISO 22 heat transfer oil will have a 5 wt % boiling point greater than
389° C. (732° F.), an ISO 32 heat transfer oil will have a
5 wt % boiling point greater than 405° C. (761° F.), an ISO
46 heat transfer oil will have a 5 wt % boiling point greater than
440° C. (824° F.), an ISO 68 heat transfer oil will have a
5 wt % boiling point greater than 468° C. (875° F.).
Preferably an ISO 100 heat transfer oil of this invention will have a 5
wt % boiling point greater than 482° C. (900° F.), more
preferably greater than 496° C. (925° F.). Wt % boiling
points are determined by ASTM D6352-04.

[0048]Embodiments of the heat transfer oils of this invention may also
comprise metals or metal oxides dispersed in them, and optionally a
dispersant. Metals, and optionally a dispersant, in the composition
provide enhanced thermal conductivity based on the presence of fine
particles. Preferred metals and dispersants for use in heat transfer oils
are taught in U.S. Patent Publication US20060027484. Preferred
embodiments of dispersant are anionic dispersant and/or nonionic
dispersant, preferably sulfo succinate, alkoxylated polyaromatics,
12-hydroxy stearic acid and/or polyhydroxy stearic acid.

[0049]Other additives that may be used in the heat transfer oils of this
invention include antioxidants, or mixtures of antioxidants, metal
deactivators, and seal and gasket swell agents.

[0050]We have invented a method to use a heat transfer oil, comprising
selecting a heat transfer oil having an auto ignition temperature greater
than 329° C. (625° F.) and a viscosity index greater than
28×Ln (Kinematic Viscosity at 100° C.)+80, wherein the heat
transfer oil comprises a base oil made From a waxy feed, providing the
heat transfer oil to a mechanical system, and transferring heat in the
mechanical system from a heat source to a heat sink.

[0051]Examples of mechanical systems where the use of the heat transfer
oil of this invention with an especially high auto ignition temperature
are valuable are heat pumps, batch reactors (especially constant heat
flux batch reactors), refrigerators, air conditioners, chemical &
pharmaceutical manufacturing equipment, and secondary loop systems.

[0052]Specific Analytical Test Methods:

[0053]Wt % Normal Paraffins in Wax-Containing Samples:

[0054]Quantitative analysis of normal paraffins in wax-containing samples
is determined by gas chromatography (GC). The GC (Agilent 6890 or 5890
with capillary split/splitless inlet and flame ionization detector) is
equipped with a flame ionization detector, which is highly sensitive to
hydrocarbons. The method utilizes a methyl silicone capillary column,
routinely used to separate hydrocarbon mixtures by boiling point. The
column is fused silica, 100% methyl silicone, 30 meters length, 0.25 mm
ID, 0.1 micron film thickness supplied by Agilent. Helium is the carrier
gas (2 ml/min) and hydrogen and air are used as the fuel to the flame.

[0055]The waxy feed is melted to obtain a 0.1 g homogeneous sample. The
sample is immediately dissolved in carbon disulfide to give a 2 wt %
solution. If necessary, the solution is heated until visually clear and
free of solids, and then injected into the GC. The methyl silicone column
is heated using the following temperature program: [0056]Initial temp:
150° C. (If C7 to C15 hydrocarbons are present, the initial
temperature is 50° C.) [0057]Ramp: 6° C. per minute
[0058]Final Temp: 400° C. [0059]Final hold: 5 minutes or until
peaks no longer elute

[0060]The column then effectively separates, in the order of rising carbon
number, the normal paraffins from the non-normal paraffins. A known
reference standard is analyzed in the same manner to establish elution
times of the specific normal-paraffin peaks. The standard is ASTM D2887
n-paraffin standard, purchased from a vendor (Agilent or Supelco), spiked
with 5 wt % Polywax 500 polyethylene (purchased from Petrolite
Corporation in Oklahoma). The standard is melted prior to injection.
Historical data collected from the analysis of the reference standard
also guarantees the resolving efficiency of the capillary column.

[0061]If present in the sample, normal paraffin peaks are well separated
and easily identifiable from other hydrocarbon types present in the
sample. Those peaks eluting outside the retention time of the normal
paraffins are called non-normal paraffins. The total sample is integrated
using baseline hold from start to end of run. N-paraffins are skimmed
from the total area and are integrated from valley to valley. All peaks
detected are normalized to 100%. EZChrom is used for the peak
identification and calculation of results.

[0062]Wt % Olefins:

[0063]The Wt % Olefins in the base oils of this invention is determined by
proton-NMR by the following steps, A-D: [0064]A. Prepare a solution of
5-10% of the test hydrocarbon in deuterochloroform. [0065]B. Acquire a
normal proton spectrum of at least 12 ppm spectral width and accurately
reference the chemical shift (ppm) axis. The instrument must have
sufficient gain range to acquire a signal without overloading the
receiver/ADC. When a 30 degree pulse is applied, the instrument must have
a minimum signal digitization dynamic range of 65,000. Preferably the
dynamic range will be 260,000 or more. [0066]C. Measure the integral
intensities between: [0067]6.0-4.5 ppm (olefin) [0068]2.2-1.9 ppm
(allylic) [0069]1.9-0.5 ppm (saturate) [0070]D. Using the molecular
weight of the test substance determined by ASTM D 2503, calculate:
[0071]1. The average molecular formula of the saturated hydrocarbons
[0072]2. The average molecular formula of the olefins [0073]3. The total
integral intensity (=sum of all integral intensities) [0074]4. The
integral intensity per sample hydrogen (=total integral/number of
hydrogens in formula) [0075]5. The number of olefin hydrogens (=olefin
integral/integral per hydrogen) [0076]6. The number of double bonds
(=olefin hydrogen times hydrogens in olefin formula/2) [0077]7. The wt %
olefins by proton NMR=100 times the number of double bonds times the
number of hydrogens in a typical olefin molecule divided by the number of
hydrogens in a typical test substance molecule.

[0078]The wt % olefins by proton NMR calculation procedure, D, works best
when the % olefins result is low, less than about 15 weight percent. The
olefins must be "conventional" olefins; i.e. a distributed mixture of
those olefin types having hydrogens attached to the double bond carbons
such as: alpha, vinylidene, cis, trans, and trisubstituted. These olefin
types will have a detectable allylic to olefin integral ratio between 1
and about 2.5. When this ratio exceeds about 3, it indicates a higher
percentage of tri or tetra substituted olefins are present and that
different assumptions must be made to calculate the number of double
bonds in the sample.

[0079]Aromatics Measurement by HPLC-UV:

[0080]The method used to measure low levels of molecules with at least one
aromatic function in the lubricant base oils of this invention uses a
Hewlett Packard 1050 Series Quaternary Gradient High Performance Liquid
Chromatography (HPLC) system coupled with a HP 1050 Diode-Array UV-Vis
detector interfaced to an HP Chem-station. Identification of the
individual aromatic classes in the highly saturated Base oils was made on
the basis of their UV spectral pattern and their elution time. The amino
column used for this analysis differentiates aromatic molecules largely
on the basis of their ring-number (or more correctly, double-bond
number). Thus, the single ring aromatic containing molecules elute first,
followed by the polycyclic aromatics in order of increasing double bond
number per molecule. For aromatics with similar double bond character,
those with only alkyl substitution on the ring elute sooner than those
with naphthenic substitution.

[0081]Unequivocal identification of the various base oil aromatic
hydrocarbons from their UV absorbance spectra was accomplished
recognizing that their peak electronic transitions were all red-shifted
relative to the pure model compound analogs to a degree dependent on the
amount of alkyl and naphthenic substitution on the ring system. These
bathochromic shifts are well known to be caused by alkyl-group
delocalization of the π-electrons in the aromatic ring. Since few
unsubstituted aromatic compounds boil in the lubricant range, some degree
of red-shift was expected and observed for all of the principle aromatic
groups identified.

[0082]Quantitation of the elating aromatic compounds was made by
integrating chromatograms made from wavelengths optimized for each
general class of compounds over the appropriate retention time window for
that aromatic. Retention time window limits for each aromatic class were
determined by manually evaluating the individual absorbance spectra of
eluting Compounds at different times and assigning them to the
appropriate aromatic class based on their qualitative similarity to model
compound absorption spectra. With few exceptions, only five classes of
aromatic compounds were observed in highly saturated API Group II and III
lubricant base oils.

[0083]HPLC-UV Calibration:

[0084]HPLC-UV is used for identifying these classes of aromatic compounds
even at very low levels. Multi-ring aromatics typically absorb 10 to 200
times more strongly than single-ring aromatics. Alkyl-substitution also
affected absorption by about 20%. Therefore, it is important to use HPLC
to separate and identify the various species of aromatics and know how
efficiently they absorb.

[0085]Five classes of aromatic compounds were identified. With the
exception of a small overlap between the most highly retained
alkyl-1-ring aromatic naphthenes and the least highly retained alkyl
naphthalenes, all of the aromatic compound classes were baseline
resolved. Integration limits for the co-eluting 1-ring and 2-ring
aromatics at 272 nm were made by the perpendicular drop method.
Wavelength dependent response factors for each general aromatic class
were first determined by constructing Beer's Law plots from pure model
compound mixtures based on the nearest spectral peak absorbances to the
substituted aromatic analogs.

[0086]For example, alkyl-cyclohexylbenzene molecules in base oils exhibit
a distinct peak absorbance at 272 nm that corresponds to the same
(forbidden) transition that unsubstituted tetralin model compounds do at
268 nm. The concentration of alkyl-1-ring aromatic naphthenes in base oil
samples was calculated by assuming that its molar absorptivity response
factor at 272 nm was approximately equal to tetralin's molar absorptivity
at 268 nm, calculated from Beer's law plots. Weight percent
concentrations of aromatics were calculated by assuming that the average
molecular weight for each aromatic class was approximately equal to the
average molecular weight for the whole base oil sample.

[0087]This calibration method was further improved by isolating the 1-ring
aromatics directly from the lubricant base oils via exhaustive HPLC
chromatography. Calibrating directly with these aromatics eliminated the
assumptions and uncertainties associated with the model compounds. As
expected, the isolated aromatic sample had a lower response factor than
the model compound because it was more highly substituted.

[0088]More specifically, to accurately calibrate the HPLC-UV method, the
substituted benzene aromatics were separated from the bulk of the
lubricant base oil using a Waters semi-preparative HPLC unit. 10 grams of
sample was diluted 1:1 in n-hexane and injected onto an amino-bonded
silica column, a 5 cm×22.4 mm ID guard, followed by two 25
cm×22.4 mm ID columns of 8-12 micron amino-bonded silica particles,
manufactured by Rainin Instruments, Emeryville, Calif., with n-hexane as
the mobile phase at a flow rate of 18 mls/min. Column eluent was
fractionated based on the detector response from a dual wavelength UV
detector set at 265 nm and 295 nm. Saturate fractions were collected
until the 265 nm absorbance showed a change of 0.01 absorbance units,
which signaled the onset of single ring aromatic elution. A single ring
aromatic fraction was collected until the absorbance ratio between 265 nm
and 295 nm decreased to 2.0, indicating the onset of two ring aromatic
elution. Purification and separation of the single ring aromatic fraction
was made by re-chromatographing the monoaromatic fraction away from the
"tailing" saturates fraction which resulted from overloading the HPLC
column.

[0091]The weight percent of all molecules with at least one aromatic
function in the purified mono-aromatic standard was confirmed via
long-duration carbon 13 NMR analysis. NMR was easier to calibrate than
HPLC UV because it simply measured aromatic carbon so the response did
not depend on the class of aromatics being analyzed. The NMR results were
translated from % aromatic carbon to % aromatic molecules (to be
consistent with HPLC-UV and D 2007) by knowing that 95-99% of the
aromatics in highly saturated lubricant base oils were single-ring
aromatics.

[0092]High power, long duration, and good baseline analysis were needed to
accurately measure aromatics down to 0.2% aromatic molecules.

[0093]More specifically, to accurately measure low levels of all molecules
with at least one aromatic function by NMR, the standard D 5292-99 method
was modified to give a minimum carbon sensitivity of 500:1 (by ASTM
standard practice E 386). A 15-hour duration run on a 400-500 MHz NMR
with a 10-12 mm Nalorac probe was used. Acorn PC integration software was
used to define the shape of the baseline and consistently integrate. The
carrier frequency was changed once during the run to avoid artifacts from
imaging the aliphatic peak into the aromatic region. By taking spectra on
either side of the carrier spectra, the resolution was improved
significantly.

[0094]Molecular Composition by FIMS:

[0095]The lubricant base oils of this invention were characterized by
Field Ionization Mass Spectroscopy (FIMS) into alkanes and molecules with
different numbers of unsaturations. The distribution of the molecules in
the oil fractions was determined by FIMS. The samples were introduced via
solid probe, preferably by placing a small amount (about 0.1 mg.) of the
base oil to be tested in a glass capillary tube. The capillary tube was
placed at the tip of a solids probe for a mass spectrometer, and the
probe was heated from about 40 to 50° C. up to 500 or 600°
C. at a rate between 50° C. and 100° C. per minute in a
mass spectrometer operating at about 10-6 torr. The mass
spectrometer was scanned from m/z 40 to m/z 1000 at a rate of 5 seconds
per decade.

[0096]The mass spectrometer used was a Micromass Time-of-Flight. Response
factors for all compound types were assumed to be 1.0, such that weight
percent was determined from area percent. The acquired mass spectra were
summed to generate one "averaged" spectrum.

[0097]The lubricant base oils of this invention were characterized by FIMS
into alkanes and molecules with different numbers of unsaturations. The
molecules with different numbers of unsaturations may be comprised of
cycloparaffins, olefins, and aromatics. If aromatics were present in
significant amounts in the lubricant base oil they would be identified in
the FIMS analysis as 4-unsaturations. When olefins were present in
significant amounts in the lubricant base oil they would be identified in
the FIMS analysis as 1-unsaturations. The total of the 1-unsaturations,
2-unsaturations, 3-unsaturations, 4-unsaturations, 5-unsaturations, and
6-unsaturations from the FIMS analysis, minus the wt % olefins by proton
NMR, and minus the wt % aromatics by HPLC-UV is the total weight percent
of molecules with cycloparaffinic functionality in the lubricant base
oils of this invention. Note that if the aromatics content was not
measured, it was assumed to be less than 0.1 wt % and not included in the
calculation for total weight percent of molecules with cycloparaffinic
functionality.

[0098]Molecules with cycloparaffinic functionality mean any molecule that
is, or contains as one or more substituents, a monocyclic or a fused
multicyclic saturated hydrocarbon group. The cycloparaffinic group may be
optionally substituted with one or more substituents. Representative
examples include, but are not limited to, cyclopropyl, cyclobutyl,
cyclopentyl, cyclohexyl, cycloheptyl, decahydronaphthalene,
octahydropentalene, (pentadecan-6-yl)cyclohexane,
3,7,10-tricyclohexylpentadecane,
decahydro-1-(pentadecan-6-yl)naphthalene, and the like.

[0099]Molecules with monocycloparaffinic functionality mean any molecule
that is a monocyclic saturated hydrocarbon group of three to seven ring
carbons or any molecule that is substituted with a single monocyclic
saturated hydrocarbon group of three to seven ring carbons. The
cycloparaffinic group may be optionally substituted with one or more
substituents. Representative examples include, but are not limited to,
cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl,
(pentadecan-6-yl) cyclohexane, and the like.

[0100]Molecules with multicycloparaffinic functionality mean any molecule
that is a fused multicyclic saturated hydrocarbon ring group of two or
more fused rings, any molecule that is substituted with one or more fused
multicyclic saturated hydrocarbon ring groups of two or more fused rings,
or any molecule that is substituted with more than one monocyclic
saturated hydrocarbon group of three to seven ring carbons. The fused
multicyclic saturated hydrocarbon ring group preferably is of two fused
rings. The cycloparaffinic group may be optionally substituted with one
or more substituents. Representative examples include, but are not
limited to, decahydronaphthalene, octahydropentalene,
3,7,10tricyclohexylpentadecane, decahydro-1-(pentadecan-6-yl)naphthalene,
and the like.

EXAMPLES

Example 1

[0101]A wax sample composed of several different batches of hydrotreated
Fischer-Tropsch wax, all made using a Co-based Fischer-Tropsch catalyst
was prepared. The different batches of wax composing the wax sample were
analyzed and all found to have the properties as shown in Table VIII.

[0102]The Co-based Fischer-Tropsch wax was hydroisomerized over a
Pt/SAPO-11 catalyst with an alumina binder. Operating conditions included
temperatures between 635° F. and 675° F. (335° C.
and 358° C.), LHSV of 1.0 hr-1, reactor pressure of about 500
psig, and once-through hydrogen rates of between 5 and 6 MSCF/bbl. The
reactor effluent passed directly to a second reactor containing a Pd on
silica-alumina hydrofinishing catalyst also operated at 500 psig.
Conditions in the second reactor included a temperature of about
350° F. (177° C.) and an LHSV of 2.0 hr-1.

[0103]The products boiling above 650° F. were fractionated by
vacuum distillation to produce distillate fractions of different
viscosity grades. Three Fischer-Tropsch derived lubricant base oils were
obtained. Two were distillate side-cut fractions (FT-4.5 and FT-6.4) and
one was a distillate bottoms fraction (FT-14). The FIMS analysis was
conducted on a Micromass Time-of-Flight spectrophotometer. The emitter on
the Micromass Time-of-Flight was a Carbotec 5 um emitter designed for Fl
operation. A constant flow of pentaflourochlorobenzene, used as lock
mass, was delivered into the mass spectrometer via a thin capillary tube.
The probe was heated from about 50° C. up to 600° C. at a
rate of 100° per minute. Test data on the three Fischer-Tropsch
derived lubricant base oils are shown in Table II, below.

[0106]HEATA and HEATB are examples of the heat transfer oils of this
invention having an auto ignition temperature greater than 625° F.
(329° C.) They both comprise a base oil, made from a waxy feed,
having a pour point less than -9° C., less than 0.3 wt %
aromatics, greater than 10 wt % total molecules with cycloparaffinic
functionality, and a ratio of molecules with monocycloparaffinic
functionality to molecules with multicycloparaffinic functionality
greater than 15, and optionally one or more lubricant additives. Their
auto ignition temperatures are both greater than an amount defined by the
equation AIT=1.6×(Kinematic Viscosity at 40° C., in
cSt)+300, in degrees Celsius. A plot of the line that defines this
preferred lower limit of auto ignition temperatures for the heat transfer
oils of this invention is shown in FIG. 1.

Example 3

[0107]Two comparative heat transfer oil blends, Comp HEATC and Comp HEATD,
were made using conventional Group II base oils. Comp HEATE is a typical
sample of Duratherm 630, of which the exact formulation is not known
other than it contains a number of additives including a dual-stage
antioxidant, metal deactivators, antifoam agent, seal & gasket extender,
and particle suspension agents. The formulations and properties of these
comparison blends are summarized in Table V.

[0108]Neither comparative examples HEATC nor HEATD had the high auto
ignition temperature of the heat transfer oils of our invention.
Comparative sample HEATE, although having a high AIT, had a lower
viscosity index and lower 5 wt % boiling point than the heat transfer
oils of our invention. Also the comparative sample HEATE, being petroleum
derived, did not have the preferred molecular composition of the heat
transfer oils of our invention.

Example 4

[0109]Three base oils, made by hydroisomerizing paraffinic Co-based
Fischer-Tropsch wax over a Pt/SAPO-11 catalyst, hydrotreating, and
distillation, were selected for blending into heat transfer oils. The
properties of the three base oils are summarized in Table VI, below.

[0110]All three of these base oils have between 10 and 70 wt % total
molecules with cycloparaffinic functionality and a ratio of molecules
with monocycloparaffinic functionality to molecules with
multicycloparaffinic functionality greater than 15. Note that FT-HN is
also an example of an isomerized Fischer-Tropsch derived base oil
fraction have a traction coefficient less than or equal to 0.015, when
measured at a kinematic viscosity of 15 cSt and at a slide to roll ratio
of 40 percent.

Example 5

[0111]The three base oils in Example 4 were blended into heat transfer oil
oils over a range of ISO viscosity grades from ISO 22 to ISO 100. The
formulations and properties of these heat transfer oils are shown in
Table VII.

[0112]The different grades of heat transfer oil were blended with base
oils made from Fischer-Tropsch wax and either with or without 0.038 wt %
antifoam agent. In these blends the Fischer-Tropsch derived base oils
that were used had weight percent aromatics less than 0.06 and weight
percent olefins less than 2.5. The Fischer-Tropsch derived base oils had
Oxidator BNs between 30 and 60 hours.

[0114]HEATG, HEATH and HEATJ were surprising in that even though they
contained a base oil, FT-HN, having a relatively high 50 wt % boiling
point (greater than 566° C. [1050° F.]), they still were
colorless by the ASTM Color test.

[0115]All of the publications, patents and patent applications cited in
this application are herein incorporated by reference in their entirety
to the same extent as if the disclosure of each individual publication,
patent application or patent was specifically and individually indicated
to be incorporated by reference in its entirety.

[0116]Many modifications of the exemplary embodiments of the invention
disclosed above will readily occur to those skilled in the art.
Accordingly, the invention is to be construed as including all structure
and methods that fall within the scope of the appended claims.